I have a bunch of white Teflon pipe thread tape. I wanted some thicker tape and the only thing I could find at the store was the usual thin white stuff for water lines and some thicker stuff that was yellowish in color and labeled for use on gas, kerosene, LPG. Doesn't say anything about water. The white stuff doesn't say what kind of liquid but does say for use on pipe threads.
I assumed there was some actual difference between the two making the white stuff unsuitable for gas lines. But I just looked at them and they are all labeled as MIL-27730A . Seems like the only difference is one is colored yellow and is a little bit thicker.
Anyone know why the one claims to be for gas when it's listed as the same mil spec as the white?
When PTFE (Teflon) tape first became available they only made it in the common single density type, which we commonly find in the hardware and home supply stores. Later they began making a double density version, which was twice as thick. Many state and local codes then adopted the double density type as mandatory when making connections for natural gas however since both products were the same color (white) it was difficult for inspectors to be sure which product had been used. PTFE tape is now made in numerous varieties and they have issued a color standard to determine which type should be used.
WHITE-Single density- should only be used on NPT threads up to 3/8 inch. YELLOW- Double Density- yellow double density is often labeled as "Gas type" RED-Triple Density: (Note-the container is red but the tape itself appears as a pale pink color). Presently required on all joints ?" diameter or greater. GREEN- Oil Free PTFE tape- Required for use on all lines conveying oxygen (I.E. -medical oxygen or welding oxygen lines). COPPER COLOR- contains granules of copper and is to be used as a thread lubricant but is not approved as a thread sealant. (Generally it is used as a thread lubricant on bolts or pipe threads for mechanical applications where no physical seal is required.)
PTFE tape is only approved as a thread seal when applied correctly. To apply you begin at the end of the pipe and wrap the tape under tension in the direction of the thread turns. Each successive layer should overlap the previous layer by ? to 2/3 and continue wrapping until the entire threaded portion of the pipe is covered. (Minimum of 3 full turns).
I was told years ago, the white stuff tends to flake off, and the flakes get into the natural gas, and clog filters and orifices. Not sure how accurate is that?
It seems to me that all teflon tapes are made of the same stuff; teflon. So, if the thin white stuff "flakes off" in the presence of natural gas, then you'd expect that every tape made of teflon would do the same, only perhaps to a greater or lesser extent.
Also, the gas piping code requires a sediment trap be installed after the gas shut-off valve but before the gas valve of each gas appliance:
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The whole idea here is that any dirt or foreign matter in the gas stream would accumulate in the trap instead of clogging up the gas valve to the appliance. If teflon tape were to "flake off", then it would be common knowledge that these traps would contain particles of teflon tape, and I've never heard of that before.
Yes, the problem is that some people allow the tape to 'overhang' the end of the threads. The first groove should be visible. Any overhang will get extruded off the connection and a string will head downstream causing problems.
I dunno. I wouldn't expect to find that in a DIY'ers work. Generally, what you find is that DIY'ers will go out of their way to do things as carefully as they can when they're working on their own house, so as to avoid problems like gas or water leaks later. They'll be as careful wrapping those threads as you would expect of anyone wanting to ensure they stand the best chance of avoiding a possible leak.
Not saying it can't happen... but I wouldn't expect that of a DIY'er working on a project in his own house.
It's more likely they will wrap the teflon in the wrong direction. Rather than forcing the tape into the threads when the fitting is screwed in, it will tend to unwrap the tape and can be messy.
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